Description:

Tree damage following dust abatement/road
stabilization treatment was evaluated on 12.5
miles of the Selway River Road, Nez Perce
National Forest. Calcium chloride was applied in
June of 2000, mostly at a rate of 51b/yd2 (18,600
lb./acre) or 6.9 lb/yd 2 (25,700 lb/acre). 1,189
trees up to 30 feet from the road were examined
in June 2001 and again in December 2001.
Western redcedar and Douglas-fir were most
damaged by the chloride. Ponderosa pine was
the most tolerant of the tree species. Severity of
damage was associated with tree species,
proximity of trees to road, and CaCl2 application
rates. Cedar foliage samples collected in
November 2001 from symptomatic trees near
treated road averaged nearly seven times more
chloride ion concentration than the controls.
Treated Douglas-fir averaged 50 times more and
ponderosa pine average 30 times more than
their respective controls. As of December 2001,
12% of cedars were dead and another 18%
appear to be dying. Douglas-fir fared worse with
29% dead and 12% dying. Grand fir and
ponderosa pine had only 6% and 4%,
respectively, dead or dying.